JP5209746B2 - High pressure pump - Google Patents

Description

  The present invention relates to a high-pressure pump used for an internal combustion engine.

Conventionally, a high-pressure pump that supplies fuel to a fuel supply system of an internal combustion engine is known. The fuel pumped up from the fuel tank is sucked into the pressurizing chamber by the lowering of the plunger in the cylinder hole of the high pressure pump, and is metered and pressurized by the raising of the plunger.
It is also known that a conventional high-pressure pump is provided with a mechanism for reducing pressure pulsation of low-pressure fuel.
Also in the high-pressure pump described in Patent Document 1, as such a fuel pressure pulsation reduction mechanism, a damper chamber (Dolk Dampfer 98 in Patent Document 1) and a variable volume chamber (Aus Greitzraum 94) are provided. (See FIGS. 2 to 5 of Patent Document 1).

DE 102004063075A1 specification

By the way, in the high-pressure pump described in Patent Document 1, the variable volume chamber (Aus Gleitzraum 94) is only covered by a part of the seal element (the Anshurach element 60) (the Oersten-Fürzen tile 64). It is. For this reason, it is affected by the heat from the high-temperature engine head installed in the vicinity of the cam that drives the reciprocating movement of the plunger, or the high-temperature lubricating oil (including engine oil) existing in the vicinity of the cam is scattered. There was a risk that the fuel in the variable volume chamber would become hot and vaporize by adhering to the seal element. When the fuel in the variable volume chamber is vaporized, it becomes difficult for the high-pressure pump to suck the fuel, and there is a problem in that the operation is disturbed.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a high-pressure pump that can ensure proper operation by suppressing high temperature of fuel in a variable volume chamber and preventing its vaporization. And

According to the first aspect of the present invention, the pump body includes a cylinder hole that accommodates the plunger so as to be reciprocally movable in the axial direction, a pressure chamber that communicates with the cylinder hole and in which fuel is pressurized by the reciprocating movement of the plunger. A low-pressure fuel passage that communicates the pressurization chamber and the fuel inlet, and a discharge passage that communicates the pressurization chamber and the fuel outlet.
The plunger has a large diameter portion and a small diameter portion. The large diameter portion is a portion that slides on the inner wall surface of the cylinder hole, and one end thereof faces the pressurizing chamber. The small diameter portion is a portion extending from the large diameter portion to the side opposite to the pressurizing chamber side. And the level | step difference surface is formed in the boundary of a large diameter part and a small diameter part. The variable volume chamber forming means is in contact with the stepped surface of the plunger and forms a variable volume chamber whose volume is variable by the reciprocating movement of the plunger. A gas chamber is disposed adjacent to the side of the variable volume chamber opposite to the cylinder hole.
Thus, the high pressure pump according to claim 1 is installed in the vicinity of the cam that drives the reciprocating movement of the plunger by disposing the gas chamber adjacent to the side opposite to the cylinder hole side of the variable volume chamber. When heat is transmitted from the high-temperature engine head to the fuel in the variable volume chamber, a gas chamber is interposed between the engine head and the variable volume chamber. For this reason, the heat from the engine head is blocked by the gas chamber.
Further, when high-temperature lubricating oil (including engine oil) existing near the cam scatters and adheres to the outer wall of the variable volume chamber forming means, the gas chamber is interposed therebetween, so that the high temperature that has been scattered Thus, the lubricating oil adheres to the outer wall of the gas chamber, and heat from the adhering high-temperature lubricating oil to the fuel in the variable volume chamber is blocked by the gas chamber.
Thus, due to the presence of the gas chamber adjacent to the variable volume chamber, the temperature increase of the fuel in the variable volume chamber is suppressed, and vaporization of the fuel is prevented. Therefore, it is possible to prevent the high-pressure pump from sucking the fuel due to the vaporization of the fuel in the variable volume chamber and causing a failure in the operation.

According to the second aspect of the present invention, the gas chamber forms a boundary with the variable volume chamber and is in contact with the fuel in the variable volume chamber, and the outer shield wall provided opposite to the inner shield wall. And a gas that fills a space between the inner shielding wall and the outer shielding wall.
Thus, the high pressure pump according to claim 2 has a gas that fills a space in which the gas chamber is sandwiched between the inner shielding wall and the outer shielding wall. The gas has an extremely low thermal conductivity as compared with metals and other solid materials mainly constituting the high-pressure pump. For this reason, heat conduction to the fuel in the variable volume chamber is effectively blocked by the gas in the gas chamber.

According to the invention which concerns on Claim 3, an inner side shielding wall consists of a member which can be elastically deformed.
Thus, in the high-pressure pump according to the third aspect, the inner shielding wall in contact with the fuel in the variable volume chamber is made of an elastically deformable member. Acts as a pulsation damper for For this reason, the pressure pulsation of the low-pressure fuel supplied from the variable volume chamber to the pressurizing chamber is reduced, and proper operation of the high-pressure pump is ensured.

According to the invention of claim 4, one end of the inner shielding wall extends in a direction perpendicular to the central axis of the cylinder hole. The wall surface on the pressurizing chamber side in the vicinity of the end portion is opposed to the step surface of the plunger, and the wall surface on the opposite side to the pressurizing chamber in the vicinity of the end portion is mounted around the small diameter portion of the plunger. The sealing member is in contact with the end of the pressurizing chamber side.
Thus, the high-pressure pump according to claim 4 is such that the inner shielding wall of the plunger is located on the side of the pressurizing chamber in the vicinity of one end of the inner shielding wall. Serves as a stopper against reciprocating movement in the cylinder bore. Similarly, the wall on the side opposite to the pressurizing chamber near the end is in contact with the end of the seal member on the pressurization chamber side, so that the inner shielding wall functions as a holder that contributes to fixing the seal member. Fulfill.
In this way, the plunger stopper used in the conventional high pressure pump becomes unnecessary, and the number of components of the high pressure pump is reduced. Therefore, the manufacturing cost of the high pressure pump can be reduced.

According to the invention which concerns on Claim 5, an outer side shielding wall is a sealing element currently fixed to the pump body. Here, the seal element is a member conventionally used in a high-pressure pump in order to fulfill the function of a holder that fixes a seal member that suppresses fuel leakage to the engine due to sliding of the plunger.
Thus, in the high pressure pump according to claim 5, since the outer shielding wall constituting the gas chamber is a seal element, the components of the conventional high pressure pump are used when a new gas chamber is provided. Increase of new parts is suppressed. Therefore, an increase in the manufacturing cost of the high pressure pump is suppressed.

According to the invention which concerns on Claim 6, an outer side shielding wall consists of a heat insulating member.
Thus, in the high-pressure pump according to the sixth aspect, when the outer shielding wall is made of a heat insulating member, when heat is to be conducted from the high-temperature engine head to the fuel in the variable volume chamber, the heat is first The heat shielding outer shielding wall blocks the conduction. Even when high-temperature lubricating oil (including engine oil) is scattered, the high-temperature lubricating oil adheres to the heat insulating outer shielding wall. The heat to be conducted to the fuel is blocked by the heat insulating outer shielding wall.
Therefore, the heat to be conducted to the fuel in the variable volume chamber is blocked not only by the gas in the gas chamber but also by the heat insulating outer shielding wall of the gas chamber. The effect | action which suppresses and prevents the vaporization is exhibited more effectively.

According to the invention which concerns on Claim 7, an inner side shielding wall is a sealing element currently fixed to the pump body.
Thus, in the high pressure pump according to claim 7, since the inner shielding wall constituting the gas chamber is a seal element, the components of the conventional high pressure pump are used when a new gas chamber is provided. Therefore, an increase in new parts is suppressed. Therefore, an increase in the manufacturing cost of the high pressure pump is suppressed.

According to the invention which concerns on Claim 8, the inner side shielding wall and the outer side shielding wall are welded, and gas is sealed by the space pinched | interposed into the inner side shielding wall and the outer side shielding wall.
Thus, in the high pressure pump according to the eighth aspect, the inner shielding wall and the outer shielding wall constituting the gas chamber are welded, and the gas is sealed in the gas chamber, so that a gas having a desired low thermal conductivity is gas. The state of filling the room is stably maintained. For this reason, the effect | action which suppresses the high temperature of the fuel in a variable volume chamber with the gas in a gas chamber, and prevents the vaporization is stably exhibited.

According to the ninth aspect of the invention, the gas in the gas chamber is nitrogen gas, helium gas, argon gas, or air.
As described above, in the high-pressure pump according to claims 1 to 8, nitrogen gas, helium gas, argon gas, or air, which has a low thermal conductivity and is easily available, is used as the gas filled in the gas chamber. Is preferred.

It is a schematic sectional drawing which shows the high pressure pump by 1st Embodiment of this invention. It is the schematic sectional drawing which expanded the plunger part enclosed by the two-point difference line of the high pressure pump of FIG. It is a schematic sectional drawing which shows the plunger part of the high pressure pump by 2nd Embodiment of this invention. It is a schematic sectional drawing which shows the plunger part of the high pressure pump by 3rd Embodiment of this invention. It is a schematic sectional drawing which shows the plunger part of the high pressure pump by 4th Embodiment of this invention.

Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
A high-pressure pump according to a first embodiment of the present invention is shown in FIG. 1, and its plunger portion is shown in FIG.
First, the high-pressure pump 1 according to the present embodiment will be described with reference to FIG.
The high-pressure pump 1 is provided in a fuel supply system that supplies fuel to the internal combustion engine. The fuel pumped up from the fuel tank is pressurized by the high-pressure pump 1 and accumulated in the delivery pipe. The fuel is injected and supplied to each cylinder of the internal combustion engine from an injector connected to the delivery pipe.
The high-pressure pump 1 includes a pump body 10, a plunger unit 20, a damper chamber 40, a suction valve unit 50, an electromagnetic drive unit 60, a discharge valve unit 70, and the like.

(A) The pump body 10 and the plunger part 20 are demonstrated.
The pump body 10 is integrally formed with a cylindrical cylinder hole 11 and a pressurizing chamber 12 communicating with the cylinder hole 11. A recess 13 is formed in a substantially annular shape around the cylinder hole 11.
The plunger portion 20 includes a plunger 21, a seal member 24, a seal element 25, a plunger spring 28, a variable volume chamber 30, and the like.

  The plunger 21 is accommodated in the cylinder hole 11 and is held so as to be capable of reciprocating in the central axis direction. The plunger 21 has one end facing the pressurizing chamber 12, a large-diameter portion 211 that slides with the inner wall constituting the cylinder hole 11, and an outer diameter smaller than the large-diameter portion 211. A small-diameter portion 212 extending from 211 to the opposite side to the pressurizing chamber 12 side. The large diameter portion 211 and the small diameter portion 212 have a coaxial shape, and a step surface 213 is formed at the boundary. A spring seat 27 is provided at the end of the plunger 21 on the small diameter portion 212 side.

  A seal member 24 is mounted around the small diameter portion 212 of the plunger 21 so as to surround the small diameter portion 212. The seal member 24 is composed of an inner peripheral Teflon ring (“Teflon” is a registered trademark) and an outer peripheral O ring that slidably contact the outer peripheral surface of the small diameter portion 212, and fuel around the small diameter portion 212. The thickness of the oil film is regulated, and the leakage of fuel to the engine due to the sliding of the plunger 21 is suppressed.

The seal element 25 is mounted around the small diameter portion 212 around the small diameter portion 212 on the spring seat 27 side of the seal member 24. The entire seal element 25 has a substantially annular shape, and a part of the seal element 25 is mounted and fixed to the recess 13 of the pump body 10. The other part of the seal element 25 is in contact with the end of the seal member 24 on the spring seat 27 side and the end on the outer peripheral side. Thus, the seal element 25 functions as a holder for fixing the seal member 24.
An oil seal 26 is attached to the end of the seal element 25 on the spring seat 27 side so as to surround the small diameter portion 212. The oil seal 26 is slidably in contact with the outer peripheral surface of the small-diameter portion 212, regulates the thickness of the oil film around the small-diameter portion 212, and suppresses oil leakage due to the sliding of the plunger 21. It is.

  A spring seat 27 is coupled to the lower portion of the plunger 21. One end of a plunger spring 28 is locked to the spring seat 27. The other end of the plunger spring 28 is locked to a predetermined end surface of the seal element 25 fixed to the pump body 10. That is, the seal element 25 also functions as a locking member for the plunger spring 28.

  Plunger springs 28 having both ends locked to the seal element 25 and the spring seat 27 function as a return spring for the plunger 21 and urge the plunger 21 against a tappet (not shown). The plunger 21 reciprocates in the axial direction in the cylinder hole 11 by contacting the cam of the camshaft via the tappet by the return spring function of the plunger spring 28. By the reciprocating movement of the plunger 21, the volume of the pressurizing chamber 12 is changed, whereby the fuel is sucked and pressurized.

  Due to the substantially annular space surrounded by the step surface 213 of the plunger 21, the outer wall of the small diameter portion 212, the inner wall constituting the cylinder hole 11 of the pump body 10, the end of the seal member 24 on the pressure chamber 12 side, and the like. A variable volume chamber 30 is formed. That is, the variable volume chamber 30 is formed by surrounding the cylinder hole 11 in a substantially annular shape. The variable volume chamber 30 communicates with the damper chamber 40 via a return passage 31 formed in the pump body 10.

  A gas chamber 32 is disposed adjacent to the variable volume chamber 30. The gas chamber 32 has an inner shielding wall 33 adjacent to the variable volume chamber 30. The inner shielding wall 33 is made of an elastically deformable member. An end portion vicinity 331 on the opposite side to the damper chamber 40 extends in a direction substantially perpendicular to the central axis of the cylinder hole 11, and an end portion vicinity 332 on the damper chamber 40 side. Extends in a direction substantially parallel to the central axis of the cylinder hole 11. In addition, the inner shielding wall 33 is welded to the inner peripheral surface of the seal element 25 at the welded portion 34a at the end portion 331 and the side wall at the other end portion 332 at the welded portion 34b. The entire circumference of the seal element 25 is welded.

The space between the inner shielding wall 33 and the seal element 25 is filled with nitrogen gas 35 and is airtight.
Thus, the gas chamber 32 is configured by the inner shielding wall 33, the sealing element 25 as the outer shielding wall, and the nitrogen gas 35 sealed in the space between the inner shielding wall 33 and the sealing element 25. .

In the vicinity of one end portion 331 of the inner shielding wall 33, the wall surface on the pressurizing chamber 12 side is opposed to the step surface 213 of the plunger 21. For this reason, the end vicinity 331 of the inner shielding wall 33 functions as a stopper when the plunger 21 reciprocates in the cylinder hole 11, particularly when it descends from the top dead center toward the bottom dead center.
Further, in the vicinity of the end portion 331 of the inner shielding wall 33, the wall surface on the spring seat 27 side is in contact with the end portion on the pressurizing chamber 12 side of the seal member 24. Therefore, the end vicinity 331 of the inner shielding wall 33 functions as a holder that contributes to fixing the seal member 24. That is, the inner shielding wall 33 in contact with the end of the seal member 24 on the pressure chamber 12 side is in contact with the end of the seal member 24 on the spring seat 27 side and the end of the outer peripheral side. And serve as a holder for fixing the seal member 24.

(B) The damper chamber 40 will be described.
The damper chamber 40 includes a recess 41, a cover 42, a damper unit 43, and the like.
The pump body 10 is provided with a recess 41 that is recessed toward the cylinder hole 11 on the opposite side of the cylinder hole 11. The concave portion 41 is covered with a bottomed cylindrical cover 42 for blocking the inside from outside air.

A damper unit 43 is disposed in the damper chamber 40. The damper unit 43 includes a pulsation damper 44 formed by joining two metal diaphragms 441 and 442, a bottom support 45 disposed on the bottom of the recess 41, and a lid support supported on the cover 42 side. 46.
In the pulsation damper 44, a gas having a predetermined pressure is sealed inside two metal diaphragms 441 and 442. The two metal diaphragms 441 and 442 are elastically deformed according to the pressure change in the damper chamber 40, thereby reducing the fuel pressure pulsation in the damper chamber 40.

A recess 47 is formed at the bottom of the recess 41 of the damper chamber 40 so as to match the bottom support 45. The bottom support portion 45 is positioned by the recess 47. In addition, although not shown in the figure, the recess 47 is formed with an inlet opening, so that fuel from the low-pressure pump is supplied to the radially inner region of the bottom support 45. That is, the fuel in the fuel tank is supplied to the damper chamber 40 from the fuel inlet through the fuel passage.
A wave spring 48 is disposed above the lid side support 46. Thereby, the wave spring 48 presses the lid-side support portion 46 toward the bottom-side support portion 45 with the cover 42 attached to the pump body 10. As a result, the pulsation damper 44 is clamped and fixed at the periphery by the lid-side support portion 46 and the bottom-side support portion 45 with an equal force in the circumferential direction.

(C) The suction valve unit 50 will be described.
The suction valve unit 50 includes a supply passage 52, a valve body 53, a seat portion 54, a suction valve 55, and the like.
The pump body 10 is provided with a cylindrical portion 51 substantially perpendicular to the central axis of the cylinder hole 11, and the inside of the cylindrical portion 51 is a fuel supply passage 52. Further, a valve body 53 is accommodated inside the cylindrical portion 51 and is fixed by a locking member. A seat portion 54 having a concave tapered circumferential surface is formed inside the valve body 53, and a suction valve 55 is disposed opposite to the seat portion 54. The suction valve 55 is guided by an inner wall of a hole provided at the bottom of the valve body 53 and reciprocates. The suction valve 55 is separated from the seat portion 54 to open the supply passage 52. When the suction valve 55 is seated on the seat portion 54, the supply passage 52 is closed.

A stopper 56 is fixed to the inner wall of the valve body 53, and this stopper 56 restricts the movement of the intake valve 55 in the valve opening direction (right direction in FIG. 1). A first spring 57 is provided between the inside of the stopper 56 and the end face of the suction valve 55. The first spring 57 attaches the suction valve 55 in the valve closing direction (left direction in FIG. 1). Rush.
The stopper 56 is formed with a plurality of inclined passages 58 that are inclined with respect to the axis of the stopper 56 in the circumferential direction. The fuel supplied through the supply passage 52 is sucked into the pressurizing chamber 12 through the inclined passage 58. The supply passage 52 communicates with the damper chamber 40 via the pressurization side passage 59.

(D) The electromagnetic drive unit 60 will be described.
The electromagnetic drive unit 60 includes a connector 61, a fixed core 62, a movable core 63, a flange 64, and the like.
The connector 61 includes a coil 611 and a terminal 612, and generates a magnetic field when the coil 611 is energized through the terminal 612. The fixed core 62 is made of a magnetic material and is accommodated inside the coil 611. The movable core 63 is made of a magnetic material and is disposed to face the fixed core 62. The movable core 63 is accommodated inside the flange 64 so as to be capable of reciprocating in the axial direction.

The flange 64 is made of a magnetic material and is attached to the cylinder portion 51 of the pump body 10. The flange 64 holds the connector 61 and the like on the pump body 10 and closes the end of the cylindrical portion 51. A cylindrical guide cylinder 65 is attached to the inner wall of the hole provided in the center of the flange 64. The cylindrical member 66 made of a nonmagnetic material prevents a magnetic short circuit between the fixed core 62 and the flange 64.
The needle 67 is formed in a substantially cylindrical shape, and is reciprocated while being guided by the inner wall of the guide cylinder 65. One end of the needle 67 is fixed to the movable core 63, and the other end can be brought into contact with the end surface of the suction valve 55 on the electromagnetic drive unit 60 side.

A second spring 68 is provided between the fixed core 62 and the movable core 63. The second spring 68 biases the movable core 63 in the valve opening direction with a force stronger than the force that the first spring 57 biases the suction valve 55 in the valve closing direction.
When the coil 611 is not energized, the movable core 63 and the fixed core 62 are separated from each other by the elastic force of the second spring 68. As a result, the needle 67 integral with the movable core 63 moves to the suction valve 55 side, and the suction valve 55 is opened when the end surface of the needle 67 presses the suction valve 55.

(E) The discharge valve unit 70 will be described.
The discharge valve unit 70 includes a discharge passage 71, a discharge valve device 80, and the like.
A discharge passage 71 is formed in the pump body 10 substantially perpendicularly to the central axis of the cylinder hole 11. The discharge passage 71 communicates with the pressurizing chamber 12 on the one hand and communicates with the fuel outlet 72 on the other hand. A discharge valve device 80 is assembled in the discharge passage 71.

The discharge valve device 80 includes a discharge valve member 82, a spring 83, an adjusting pipe 84, and the like.
The discharge valve member 82 is accommodated relative to the valve seat 85 of the pump body 10.

A spring 83 as an urging member is accommodated on the fuel outlet 72 side of the discharge valve member 82. One end of the spring 83 is in contact with the second end surface of the discharge valve member 82. A cylindrical adjusting pipe 84 is accommodated on the fuel outlet 72 side of the spring 83. The adjusting pipe 84 is engaged with the other end of the spring 83 as a support member.
Thus, the discharge valve member 82, the spring 83, and the adjusting pipe 84 are provided, and the discharge valve member 82 is biased by the biasing force of the spring 83 whose end is locked to the adjusting pipe 84. 80 is assembled to the discharge valve portion 70.

Thus, the discharge valve apparatus 80 assembled | attached to the discharge valve part 70 operate | moves as follows.
As the plunger 21 rises in the cylinder hole 11, the fuel pressure in the pressurizing chamber 12 rises. The force received by the discharge valve member 82 from the fuel on the pressure chamber 12 side (upstream side) of the discharge valve member 82 of the discharge valve device 80 is the elastic force of the spring 83 and the fuel outlet 72 side (from the discharge valve member 82). When greater than the sum of the forces received from the fuel on the downstream side, the discharge valve member 82 separates from the valve seat 85 of the pump body 10. That is, the discharge valve device 80 is opened. As a result, the high-pressure fuel pressurized in the pressurizing chamber 12 is discharged to the fuel outlet 72 through the discharge passage 71.

On the other hand, as the plunger 21 descends in the cylinder hole 11, the fuel pressure in the pressurizing chamber 12 decreases. When the force received by the discharge valve member 82 from the fuel on the upstream side is equal to or smaller than the sum of the elastic force of the spring 83 and the force received from the fuel on the downstream side, the discharge valve member 82 becomes the valve seat 85 of the pump body 10. Sit on. That is, the discharge valve device 80 is closed. This prevents fuel downstream from the discharge valve member 82 from flowing back into the upstream pressurizing chamber 12.
Thus, the valve member device 80 assembled to the discharge valve portion 70 functions as a check valve for high-pressure fuel discharged from the pressurizing chamber 12 toward the fuel outlet 72.

Next, the operation of the high-pressure pump 1 will be described.
(1) Suction stroke When the plunger 21 descends from the top dead center toward the bottom dead center in the cylinder hole 11 due to the rotation of the camshaft, the volume of the pressurizing chamber 12 increases, and the fuel in the pressurizing chamber 12 Depressurized. At this time, in the discharge valve portion 70, the discharge valve member 82 of the discharge valve device 80 is seated on the valve seat 85 and closes the discharge passage 71. Further, in the suction valve section 50, the suction valve 55 moves to the right in FIG. 1 against the urging force of the first spring 57 due to the pressure difference between the pressurizing chamber 12 and the supply passage 52, and the valve is opened. It becomes a state. At this time, since the energization of the coil 611 of the electromagnetic drive unit 60 is stopped, the movable core 63 and the needle 67 integral with the movable core 63 move to the right in FIG. 1 by the urging force of the second spring 68. . Accordingly, the needle 67 and the suction valve 55 come into contact with each other, and the suction valve 55 maintains the open state. As a result, fuel is sucked into the pressurizing chamber 12 from the supply passage 52.

In the suction stroke, the volume of the variable volume chamber 30 decreases due to the lowering of the plunger 21. Accordingly, the fuel in the variable volume chamber 30 is sent out to the damper chamber 40 via the return passage 31.
Here, the cross-sectional area ratio between the large diameter portion 211 and the variable volume chamber 30 is approximately 1: 0.6. Therefore, the ratio of the increase in the volume of the pressurizing chamber 12 to the decrease in the volume of the variable volume chamber 30 is also 1: 0.6. For this reason, about 60% of the fuel sucked into the pressurizing chamber 12 is supplied from the variable volume chamber 30, and the remaining about 40% is sucked from the fuel inlet. Thereby, the fuel suction efficiency into the pressurizing chamber 12 is improved.

(2) Metering stroke When the plunger 21 moves up from the bottom dead center toward the top dead center in the cylinder hole 11 due to the rotation of the camshaft, the volume of the pressurizing chamber 12 decreases. At this time, since energization to the coil 611 is stopped until a predetermined time, the needle 67 and the suction valve 55 are positioned in the right direction in FIG. 1 by the urging force of the second spring 68. As a result, the supply passage 52 is kept open. For this reason, the low-pressure fuel once sucked into the pressurizing chamber 12 is returned to the supply passage 52. Therefore, the pressure in the pressurizing chamber 12 does not increase.

In the metering stroke, the volume of the variable volume chamber 30 increases as the plunger 21 rises. Accordingly, the fuel in the damper chamber 40 flows into the variable volume chamber 30 via the return passage 31.
At this time, about 60% of the volume of the low-pressure fuel discharged from the pressurizing chamber 12 to the damper chamber 40 is sucked into the variable volume chamber 30 from the damper chamber 40. This reduces about 60% of the fuel pressure pulsation.

(3) Pressurization stroke The coil 611 is energized at a predetermined time while the plunger 21 rises in the cylinder hole 11 from the bottom dead center toward the top dead center. Then, a magnetic attractive force is generated between the fixed core 62 and the movable core 63 by the magnetic field generated in the coil 611. When the magnetic attraction force becomes larger than the difference between the elastic force of the second spring 68 and the elastic force of the first spring 57, the movable core 63 and the needle 67 move to the fixed core 72 side (left direction in FIG. 1). Thereby, the pressing force of the needle 67 against the suction valve 55 is released. The suction valve 55 moves to the seat portion 54 side by the elastic force of the first spring 57 and the force generated by the flow of low-pressure fuel discharged from the pressurizing chamber 12 to the damper chamber 40 side. Accordingly, the suction valve 55 is seated on the seat portion 54 and the supply passage 52 is closed.

From when the intake valve 55 is seated on the seat portion 54, the fuel pressure in the pressurizing chamber 12 increases as the plunger 21 rises toward the top dead center. In the discharge valve portion 70, the force that the upstream fuel pressure acts on the discharge valve member 82 of the discharge valve device 80 is the force that the downstream fuel pressure acts on the discharge valve member 82 and the spring 83. When it becomes larger than the sum of the urging forces, the discharge valve member 82 opens. As a result, the high-pressure fuel pressurized in the pressurizing chamber 12 is discharged from the fuel outlet 72 via the discharge passage 71.
Note that energization of the coil 611 is stopped during the pressurization stroke. Since the force that the fuel pressure in the pressurizing chamber 12 acts on the suction valve 55 is larger than the urging force of the second spring 68, the suction valve 55 maintains the closed state.

The high-pressure pump 1 repeats (1) the intake stroke, (2) the metering stroke, and (3) the pressurization stroke to pressurize and discharge a necessary amount of fuel to the internal combustion engine.
If the timing of energizing the coil 611 is advanced, the time of the metering stroke is shortened and the time of the pressurizing stroke is lengthened. As a result, the amount of fuel returned from the pressurizing chamber 12 to the supply passage 52 decreases, and the amount of fuel discharged from the discharge passage 71 increases. On the other hand, if the timing of energizing the coil 611 is delayed, the time of the metering stroke becomes longer and the time of the discharge stroke becomes shorter. Thereby, the fuel returned from the pressurizing chamber 12 to the supply passage 52 increases, and the fuel discharged from the discharge passage 71 decreases.
Thus, by controlling the timing of energizing the coil 611, the amount of fuel discharged from the high-pressure pump 1 is controlled to the amount required by the internal combustion engine.

Next, the effect of this embodiment is demonstrated.
In the present embodiment, a gas chamber 32 is disposed adjacent to the variable volume chamber 30 of the high-pressure pump 1, and the gas chamber 32 serves as an inner shielding wall 33 and an outer shielding wall adjacent to the variable volume chamber 30. The seal element 25 and the nitrogen gas 35 sealed in a space between the inner shielding wall 32 and the seal element 25 are configured. For this reason, even if heat from a high-temperature engine head installed in the vicinity of the cam that drives the reciprocating movement of the plunger is to be conducted to the fuel in the variable volume chamber, the nitrogen gas 35 in the gas chamber 32 interposed in the middle thereof. Thus, the influence of heat from the high-temperature engine head is blocked. Also, high temperature lubricating oil (including engine oil) scatters from the vicinity of the cam and adheres to the outer wall of the seal element 25, and heat from the adhered high temperature lubricating oil attempts to conduct to the fuel in the variable volume chamber. The influence of heat from the attached high-temperature lubricating oil is blocked by the nitrogen gas 35 in the gas chamber 32 interposed in the middle.
Here, the nitrogen gas 35 in the gas chamber 32 has a thermal conductivity of 25.76 mW / (m · K) under the conditions of a temperature of 25 ° C. and an atmospheric pressure of 1 atm. Since it is extremely low as compared with the solid material, the effect of blocking the heat conduction to the fuel in the variable volume chamber 30 is sufficiently large.

Further, the inner shielding wall 33 constituting the gas chamber 32 is welded to the inner peripheral surface of the seal element 25 at the welded portion 34a at the end portion 331 and is welded to the inner peripheral surface of the seal element 25. Is welded to the inner peripheral surface of the seal element 25 at the welded portion 34b. Thereby, the nitrogen gas 35 in the gas chamber 32 is hermetically sealed. For this reason, the heat conduction blocking action by the nitrogen gas 35 in the gas chamber 32 is stably maintained.
Thus, the heat conduction action by the nitrogen gas 35 in the gas chamber 32 adjacent to the variable volume chamber 30 prevents the fuel in the variable volume chamber 30 from becoming hot and prevents the fuel from vaporizing. Therefore, it is possible to prevent an operation failure of the high pressure pump 1 that makes it difficult to suck the fuel of the high pressure pump 1 due to vaporization of the fuel in the variable volume chamber 30.

Further, the high-pressure pump 1 of the present embodiment, when repeating the suction, metering, and pressurization strokes of (1) to (3), the fuel in the variable volume chamber 30 is changed as the plunger 21 is lowered and raised. , Sent to the damper chamber 40 and returned from the damper chamber 40. At this time, the elastically deformable inner shielding wall 33 interposed between the fuel in the variable volume chamber 30 and the nitrogen gas 35 in the gas chamber 32 functions as a pulsation damper for the fuel in the variable volume chamber 30. To do. For this reason, the pressure pulsation of the fuel in the variable volume chamber 30 is reduced.
Thus, the fuel pressure pulsation reducing action by the inner shielding wall 33 functioning as a pulsation damper with respect to the fuel in the variable volume chamber 30 is combined with the fuel pressure pulsation reducing action by the damper chamber 40, and the low pressure fuel supplied to the pressurizing chamber 12. The effect of further reducing the pressure pulsation can be obtained, and the proper operation of the high-pressure pump 1 can be ensured.

  Further, in the vicinity of the end 331 of the inner shielding wall 33 constituting the gas chamber 32, the wall surface on the pressurizing chamber 12 side is opposed to the step surface 213 of the plunger 21, and the wall surface on the opposite side to the pressurizing chamber 12 is the sealing member 24. Is in contact with the end of the pressurizing chamber 12 side. For this reason, the inner shielding wall 33 functions as a stopper when the plunger 21 reciprocates in the cylinder hole 11 on the one hand, and on the other hand, the end of the seal member 24 on the spring seat 27 side and the small diameter portion 212. It is integrated with the seal element 25 in contact with the outer peripheral portion on the opposite side, and functions as a holder for fixing the seal member 24.

In other words, the inner shielding wall 33 constituting the gas chamber 32 fulfills the function of the plunger stopper in the conventional high-pressure pump. For this reason, the high-pressure pump 1 does not require a plunger stopper used in a conventional high-pressure pump. Therefore, the number of components of the high-pressure pump 1 can be reduced, and the manufacturing cost of the high-pressure pump 1 can be reduced.
Further, as the outer shielding wall constituting the gas chamber 32, the seal element 25, which is a conventional component used in the high-pressure pump, is used, thereby increasing the number of new parts required when the gas chamber 32 is disposed. Is suppressed. Therefore, an increase in manufacturing cost of the high-pressure pump 1 can be suppressed.

(Second Embodiment)
The plunger part of the high-pressure pump according to the second embodiment of the present invention is shown in FIG. In the following embodiments, the same reference numerals are given to substantially the same components as those in the first embodiment, and the description thereof is omitted.
First, the plunger part 20 of the high-pressure pump 2 according to the present embodiment will be described with reference to FIG. In addition, since parts other than the plunger part 20 have the same configuration as the high-pressure pump 1 shown in FIG. 1 of the first embodiment, the description thereof is omitted.
As in the case of the first embodiment, the plunger portion 20 includes a plunger 21, a seal member 24, a seal element 25, a plunger spring 28, a variable volume chamber 30, and the like.

A gas chamber 32A adjacent to the variable volume chamber 30 of the high-pressure pump 2 according to the present embodiment has an inner shielding wall 33A instead of the inner shielding wall 33 of the first embodiment. As in the case of the first embodiment, the inner shielding wall 33A is made of an elastically deformable member and functions as a pulsation damper for the fuel in the variable volume chamber 30.
The inner shielding wall 33A has an end portion 331a on the side opposite to the damper chamber 40 extending in a direction substantially perpendicular to the central axis of the cylinder hole 11 as in the case of the first embodiment. The side wall of the vicinity 331a is welded to the inner peripheral surface of the seal element 25 by the same welded portion 34a as in the first embodiment. On the other hand, the end portion vicinity 332a of the inner shielding wall 33A on the damper chamber 40 side extends in a direction substantially perpendicular to the central axis of the cylinder hole 11 unlike the case of the first embodiment, and the side wall of the end portion vicinity 332a is The entire circumference is welded to the inner circumferential surface of the seal element 25 at a welded portion 34c different from the welded portion 34b of the first embodiment.

A nitrogen gas 35 is sealed in a space between the inner shielding wall 33A and the sealing element 25 as the outer shielding wall, as in the case of the first embodiment.
Thus, the inner shielding wall 33A having a shape different from that of the inner shielding wall 33 of the first embodiment, the sealing element 25 as the outer shielding wall, and the space between the inner shielding wall 33A and the sealing element 25 are sealed. The gas chamber 32 </ b> A of the present embodiment is configured from the nitrogen gas 35 that is generated.

In the vicinity of the end 331a of the inner shielding wall 33A constituting the gas chamber 32A, the wall surface on the pressurizing chamber 12 side faces the step surface 213 of the plunger 21 as in the case of the first embodiment, and the pressurizing chamber 12 The wall surface on the opposite side is in contact with the end of the sealing member 24 on the pressure chamber 12 side. For this reason, 33 A of inner side shielding walls fulfill | perform the function similar to the function which a plunger stopper performs like the case of the said 1st Embodiment.
In addition, since the part of the plunger part 20 other than the gas chamber 32A has the same configuration as that in the case of the first embodiment, the description thereof is omitted.

Next, the effect of this embodiment is demonstrated.
In the present embodiment, the gas chamber 32A disposed adjacent to the variable volume chamber 30 of the high-pressure pump 2 includes an inner shielding wall 32A adjacent to the variable volume chamber 30, a sealing element 25 serving as an outer shielding wall, and The nitrogen gas 35 is sealed in a space between the inner shielding wall 32A and the seal element 25.
For this reason, in the present embodiment, as in the case of the first embodiment, the heat conduction of the nitrogen gas 35 in the gas chamber 32A is suppressed, so that the fuel in the variable volume chamber 30 is prevented from being heated at a high temperature. Therefore, it is possible to prevent an operation failure of the high-pressure pump 2 due to vaporization.

In the present embodiment, the shape of the inner shielding wall 33A of the gas chamber 32A and the welded portion 34c with the sealing element 25 are the same as the shape of the inner shielding wall 33 of the gas chamber 32 and the sealing element 25 of the first embodiment. It is different from the welded part 34b.
That is, the vicinity of the end portion 332 of the inner shielding wall 33 of the gas chamber 32 of the first embodiment extends in a direction substantially parallel to the central axis of the cylinder hole 11, and the side wall of the end portion vicinity 332 is sealed by the welded portion 34 b. Whereas the entire periphery is welded to the inner peripheral surface of the element 25, the vicinity 332a of the inner shielding wall 33A of the gas chamber 32A of the present embodiment extends in a direction substantially perpendicular to the center axis of the cylinder hole 11, The side wall of the end vicinity 332a is welded to the inner peripheral surface of the seal element 25 by the welded portion 34c.

As described above, the inner shielding wall 33A has a shape different from the shape of the inner shielding wall 33 of the first embodiment, so that the volume of the gas chamber 32A is relatively large as is apparent from the comparison between FIG. 2 and FIG. Therefore, the volume of the nitrogen gas 35 sealed therein is relatively increased. For this reason, the heat conduction blocking action by the nitrogen gas 35 in the gas chamber 32A is greater than in the case of the first embodiment. Accordingly, it is possible to more effectively prevent an operation failure of the high-pressure pump 1 due to the vaporization of the fuel in the variable volume chamber 30.
Note that the pressure of the low-pressure fuel supplied to the pressurizing chamber 12 due to the other effects of the present embodiment, for example, the fuel pressure pulsation reducing action of the inner shielding wall 33A that functions as a pulsation damper for the fuel in the variable volume chamber 30. The effects contributing to the reduction of pulsation are the same as in the case of the first embodiment.

(Third embodiment)
The plunger part of the high-pressure pump according to the third embodiment of the present invention is shown in FIG.
First, the plunger portion 20 of the high-pressure pump 3 according to the present embodiment will be described with reference to FIG. In addition, since parts other than the plunger part 20 have the same configuration as the high-pressure pump 1 shown in FIG. 1 of the first embodiment, the description thereof is omitted.
As in the case of the first embodiment, the plunger portion 20 includes a plunger 21, a seal member 24, a seal element 25, a plunger spring 28, a variable volume chamber 30, and the like. However, unlike the case of the first embodiment, a plunger stopper 23 is provided in the ranger portion 20 of the present embodiment.

  The plunger stopper 23 is disposed in a substantially annular shape around the small diameter portion 212 of the plunger 21. A concave portion that is recessed toward the spring seat 27 is formed on the end surface of the plunger stopper 23 on the pressure chamber 12 side. An end surface 231 facing the pressurizing chamber 12 in the outer portion of the recess is connected and fixed to the pump body 10, and an end surface 232 facing the pressurizing chamber 12 in the inner portion of the recess is fixed to the plunger 21. The large-diameter portion 211 and the small-diameter portion 212 are opposed to the step surface 213.

Thus, the end surface 232 of the plunger stopper 23 fixed to the pump body 10 that faces the stepped surface 213 of the plunger 21 moves from the top dead center to the bottom dead center when the plunger 21 reciprocates in the cylinder hole 11. It functions as a stopper when descending.
The plunger stopper 23 is formed with a plurality of grooves extending from the inside of the recess to the outer edge. The region between the step surface 213 of the plunger 21 and the plunger stopper 23 in the variable volume chamber 30 communicates with the region communicating with the damper chamber 40 by the plurality of grooves.

A seal member 24 is mounted around the small diameter portion 212 around the small diameter portion 212 closer to the spring seat 27 than the plunger stopper 23. The wall surface of the plunger stopper 23 on the spring seat 27 side is in contact with the end of the seal member 24 on the pressure chamber 12 side. For this reason, the plunger stopper 23 is integrated with the seal element 25 that is in contact with the end portion on the spring seat 27 side and the end portion on the outer peripheral side of the seal member 24, and functions as a holder for fixing the seal member 24.
The seal element 25, the plunger spring 28, the variable volume chamber 30 and the like are arranged in the same manner as in the first embodiment.

The gas chamber 32B adjacent to the variable volume chamber 30 of the high-pressure pump 3 according to the present embodiment has an inner shielding wall 33B instead of the inner shielding wall 33 of the first embodiment. As in the case of the first embodiment, the inner shielding wall 33B is made of an elastically deformable member and functions as a pulsation damper for the fuel in the variable volume chamber 30.
The inner shielding wall 33B has an end portion 331b on the side opposite to the damper chamber 40 extending in a direction substantially parallel to the central axis of the cylinder hole 11 unlike the case of the first embodiment. The side wall of 331b is welded to the inner peripheral surface of the seal element 25 at the same welded portion 34a as in the first embodiment.
In the present embodiment, since the plunger stopper 23 is provided, the shape of the end portion vicinity 331b of the inner shielding wall 33B is different from that in the first embodiment. For example, the side wall of the inner shielding wall 33 </ b> B near the end 331 b is in contact with the outer peripheral surface of the plunger stopper 23.

On the other hand, the vicinity 332b of the inner shielding wall 33B on the damper chamber 40 side extends in a direction substantially parallel to the central axis of the cylinder hole 11 as in the case of the first embodiment, and the side wall of the end vicinity 332b is The entire circumference is welded to the inner circumferential surface of the seal element 25 at the same welded portion 34b as in the first embodiment.
Further, a nitrogen gas 35 is sealed in a space between the inner shielding wall 33B and the sealing element 25 as the outer shielding wall, as in the case of the first embodiment.
Thus, the gas chamber 32B of the present embodiment is composed of the inner shielding wall 33B, the sealing element 25 as the outer shielding wall, and the nitrogen gas 35 sealed in the space sandwiched between the inner shielding wall 33B and the sealing element 25. Composed.

Next, the effect of this embodiment is demonstrated.
In the present embodiment, the gas chamber 32B disposed adjacent to the variable volume chamber 30 of the high-pressure pump 3 includes an inner shielding wall 33B adjacent to the variable volume chamber 30, a seal element 25 as an outer shielding wall, and It is composed of nitrogen gas 35 sealed in a space between the inner shielding wall 33B and the sealing element 25.

For this reason, in the present embodiment, similarly to the case of the first embodiment, the heat conduction of the nitrogen gas 35 in the gas chamber 32B is suppressed, so that the fuel in the variable volume chamber 30 is prevented from being heated at a high temperature. It is possible to prevent an operational failure of the high-pressure pump 3 due to the vaporization of.
Similarly to the case of the first embodiment, the elastically deformable inner shielding wall 33B of the gas chamber 32B functions as a pulsation damper, and exerts a fuel pressure pulsation reducing action on the fuel in the variable volume chamber 30. This can contribute to reduction of pressure pulsation of the low-pressure fuel supplied to the pressurizing chamber 12.

  However, in the present embodiment, a plunger stopper 23 is provided, and this plunger stopper 23 functions as a stopper for reciprocating movement of the plunger 21 and a holder for fixing the seal member 24 integrally with the seal element 25. . For this reason, the same function that the inner shielding wall 33 of the first embodiment had is not the inner shielding wall 33B of the present embodiment.

  From the above, even in the high-pressure pump 3 in which the plunger stopper 23 is disposed, the present embodiment is used as the inner shielding wall 33B and the outer shielding wall that function as a pulsation damper adjacent to the variable volume chamber 30. By providing the gas chamber 32B composed of the sealing element 25 and the nitrogen gas 35 sealed in the space between them, the same operational effects as in the case of the first embodiment can be obtained. Can do.

(Fourth embodiment)
FIG. 5 shows the plunger portion of the high-pressure pump according to the second embodiment of the present invention. First, the plunger portion 20 of the high-pressure pump 4 according to this embodiment will be described with reference to FIG. In addition, since parts other than the plunger part 20 have the same configuration as the high-pressure pump 1 shown in FIG. 1 of the first embodiment, the description thereof is omitted.
As in the case of the third embodiment, the plunger portion 20 includes a plunger 21, a plunger stopper 23, a seal member 24, a seal element 25, a plunger spring 28, a variable volume chamber 30, and the like.

  The gas chamber 32C adjacent to the variable volume chamber 30 of the high-pressure pump 4 according to the present embodiment has a sealing element 25 as an inner shielding wall instead of the inner shielding wall 33B of the third embodiment, and is also an outer shielding wall. Instead of the sealing element 25, an outer shielding wall 36 is provided. This outer shielding wall 36 is made of a heat insulating member, and an end portion vicinity 361 on the side opposite to the damper chamber 40 extends in a direction substantially parallel to the central axis of the cylinder hole 11, and an end portion vicinity 362 on the damper chamber 40 side is formed. It extends in a direction substantially perpendicular to the central axis of the cylinder hole 11. The side wall of one end vicinity 361 is welded to the inner circumferential surface of the seal element 25 at the welded portion 34d, and the side wall of the other end portion 362 is welded to the seal element 25 at the welded portion 34e. The entire circumference is welded to the inner circumference.

A nitrogen gas 35 is sealed in a space between the sealing element 25 as the inner shielding wall and the outer shielding wall 36.
Thus, the gas chamber 32C of the present embodiment is configured from the sealing element 25 as the inner shielding wall, the outer shielding wall 36, and the nitrogen gas 35 sealed in the space sandwiched between the sealing element 25 and the outer shielding wall 36. Is done.
In addition, since parts other than the gas chamber 32C in the plunger portion 20 have the same configuration as in the case of the third embodiment, the description thereof is omitted.

Next, the effect of this embodiment is demonstrated.
In the present embodiment, the gas chamber 32C disposed adjacent to the variable volume chamber 30 of the high-pressure pump 4 includes a sealing element 25 as an inner shielding wall, an outer shielding wall 36 made of a heat insulating member, and these The nitrogen gas 35 is sealed in a space between the seal element 25 and the outer shielding wall 36.

For this reason, in the present embodiment, as in the case of the third embodiment, it is possible to achieve a heat conduction blocking action by the nitrogen gas 35 in the gas chamber 32C, resulting from the vaporization of the fuel in the variable volume chamber 30. An operation failure of the high-pressure pump 4 can be prevented.
In addition, since the outer shielding wall 36 is made of a heat insulating member, the heat conduction blocking action by the outer shielding wall 36 is added to the heat conduction blocking action by the nitrogen gas 35, so that the total heat conduction blocking effect by the gas chamber 32C is obtained. As a result, the operation failure of the high-pressure pump 4 can be prevented more effectively.

(Other embodiments)
In the said 1st-4th embodiment, although the nitrogen gas 35 is used as gas sealed in the gas chambers 32, 32A, 32B, 32C, it is not limited to nitrogen gas. For example, helium gas, argon gas, or air may be used. These gases all have extremely low thermal conductivity as compared with metals and other solid materials mainly constituting the high-pressure pumps 1, 2, 3, and 4.
In addition, when using air, it is not necessary to seal in the gas chambers 32, 32A, 32B, and 32C. For this reason, when the inner shielding walls 33, 32 </ b> A, 32 </ b> B and the outer shielding wall 36 are coupled and fixed to the seal element 25, it is possible to use another method instead of the entire circumference welding method.

1, 2, 3, 4 ... high pressure pump 10 ... pump body 11 ... cylinder hole 12 ... pressurizing chamber 20 ... plunger part 21 ... plunger 23 ... plunger stopper 24 .... Seal member 25 ... Seal element 30 ... Variable volume chamber 31 ... Return passages 32, 32A, 32B, 32C ... Gas chambers 33, 33A, 33B ... Inner shielding walls 331, 331a, 331b ... near the end 332, 332a, 332b ... near the end 34a, 34b, 34c, 34d, 34e ... weld 35 ... nitrogen gas 36 ... outer shielding walls 361, 362 ... · Near end 40 · · · damper chamber 50 · · · intake valve portion 60 · · · electromagnetic drive portion 70 · · · discharge valve portion

Claims (9)

A plunger,
A cylinder hole that accommodates the plunger so as to be reciprocally movable in the axial direction, a pressure chamber that communicates with the cylinder hole, and pressurizes fuel by reciprocating movement of the plunger, and a low pressure that communicates the pressure chamber and the fuel inlet A pump body having a side fuel passage, and a discharge passage communicating the pressurizing chamber and the fuel outlet;
A step surface between a large-diameter portion where one end of the plunger faces the pressurizing chamber and slides on the inner wall surface of the cylinder hole and a small-diameter portion extending from the large-diameter portion to the opposite side of the pressurizing chamber. A variable volume chamber forming means for forming a variable volume chamber that is provided in contact with the plunger and whose volume is variable by reciprocating movement of the plunger;
A gas chamber provided adjacent to the side opposite to the cylinder hole side of the variable volume chamber;
A high pressure pump comprising:   The gas chamber forms a boundary with the variable volume chamber, contacts an inner shielding wall with fuel in the variable volume chamber, an outer shielding wall provided facing the inner shielding wall, the inner shielding wall, and the The high-pressure pump according to claim 1, further comprising: a gas filling a space sandwiched between the outer shielding walls.   The high-pressure pump according to claim 2, wherein the inner shielding wall is made of an elastically deformable member.   The inner shielding wall has one end portion extending in a direction perpendicular to the central axis of the cylinder hole, and the wall surface on the pressure chamber side in the vicinity of the end portion is opposed to the step surface of the plunger. The wall surface on the opposite side to the pressurizing chamber in the vicinity of the end portion is in contact with the end portion on the pressurizing chamber side of the seal member mounted around the small diameter portion of the plunger. Item 4. The high-pressure pump according to Item 2 or 3.   The high-pressure pump according to any one of claims 2 to 4, wherein the outer shielding wall is a seal element fixed to the pump body.   The high-pressure pump according to claim 2, wherein the outer shielding wall is made of a heat insulating member.   The high-pressure pump according to claim 2 or 6, wherein the inner shielding wall is a sealing element fixed to the pump body.   The inner shielding wall and the outer shielding wall are welded, and the gas is sealed in a space sandwiched between the inner shielding wall and the outer shielding wall. The high pressure pump according to claim 1.   The high-pressure pump according to any one of claims 2 to 8, wherein the gas is nitrogen gas, helium gas, argon gas, or air.

Images